1. Field of the Invention
The present invention relates to an inspecting apparatus and an image pickup apparatus which inspect a pattern or the like of a photomask or a wafer used in manufacturing a semiconductor device.
2. Description of the Related Art
As an inspecting apparatus applied to the steps in manufacturing a semiconductor device, a photomask
inspection apparatus which inspects a mask pattern of a photomask is known (for example, see Jpn. Pat. Appln. KOKAI Publication No. 11-72905).
FIG. 6 is a diagram for explaining an example of the configuration of a photomask inspection apparatus 10. The photomask inspection apparatus 10 includes a mask image capturing device 20, a reference data generating device 30, and a data comparing circuit 40.
The mask image capturing device 20 includes a laser beam source 21, an illuminating optical system 22 which uniforms a beam from the laser beam source 21 to irradiate the beam onto a photomask M, a condenser lens 23 which guides a beam from the illuminating optical system 22 to the photomask M, a stage 24 on which the photomask M is placed, a stage drive mechanism 25 which moves the stage 24 in an accumulating direction (direction of an arrow X in FIG. 6) perpendicular to an irradiating direction of the stage 24, an object lens 26 to focus a beam transmitted through the photomask M on a TDI (Time Delay and Integration) sensor 27 (to be described later), and the TDI sensor 27 on which pixels are arranged in the accumulating direction and a pixel direction perpendicular to each other. Image data D1 of the photomask M is output from the TDI sensor 27.
The reference data generating device 30 includes a reference data generating circuit 31 which generates C reference data on the basis of design data of the photomask M to output reference data D2 for the photomask. The data comparing circuit 40 has a function that compares the image data D1 of the photomask M with the reference data D2, outputs comparison data D3 on the basis of the result of the comparison, and detects a defect P.
The photomask inspecting apparatus described above has the following problem. That is, the pattern of the photomask is micropatterned to shorten the wavelength of the laser beam source, and the intensity of the beam input to the sensor becomes low. The TDI sensor is an accumulative line sensor, and a weak beam can be amplified by the number of accumulating layers. For this reason, the photomask inspecting apparatus is suitable for highly accurate photomask inspection.
However, when the moving speed of the stage is not matched with accumulating time, an image is blurred disadvantageously. For this reason, in order to cause the TDI sensor to pick up the image of the photomask, image pickup must be performed such that the stage moving speed is determined in accordance with the accumulating time of the TDI sensor. The stage speed calculated on the basis of the accumulating time is not matched with an actual stage moving speed, a blurred image is obtained. For this reason, the accumulating time of the TDI sensor is varied such that the position of the stage can be monitored, and the TDI sensor picks up the image of the photomask while synchronizing positions. The fluctuation in speed in the accumulating direction of the TDI sensor is improved.
On the other hand, even though the stage moves in the pixel direction perpendicular to the accumulating direction, a blurred image or a distorted image is disadvantageously formed. Even though the accumulating time of the TDI sensor is made variable, the problem cannot be solved.